Podcast: Antioxidant vitamin and mineral supplements to prevent the development of age-related macular degeneration (AMD)

Age-related macular degeneration is a progressive and sight-threatening disease affecting the central area of the retina. Two updated Cochrane Reviews from July 2017 present the evidence for the use of antioxidant vitamin and mineral supplements to prevent it or slow down progression. Lead author, Jenny Evans from the London School of Hygiene and Tropical Medicine in the UK tells us more in this podcast.

John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. Age-related macular degeneration is a progressive and sight-threatening disease affecting the central area of the retina. Two updated Cochrane Reviews from July 2017 present the evidence for the use of antioxidant vitamin and mineral supplements to prevent it or slow down progression. Lead author, Jenny Evans from the London School of Hygiene and Tropical Medicine in the UK tells us more in this podcast.

Jenny: Age-related macular degeneration, or AMD, affects many people across the world. Approximately, one in three people over 80 years of age have early signs of the disease.One theory as to why AMD develops relates to “oxidative stress” in the retina, which means that taking anti-oxidant vitamins, such as vitamin C, E carotenoids and zinc might help by reducing this stress and avoiding the cellular damage. Our pair of Cochrane Reviews examine whether antioxidant vitamins and mineral supplements, including lutein and zeaxanthin, can prevent the development of AMD or slow down its progression, and include a total of 24 studies.Five large studies had compared taking vitamin E, beta-carotene, vitamin C and multivitamin with taking a placebo in people in the general population who did not have AMD. More than 75,000 people were randomised in these studies. They were followed for 4 to 10 years, and people taking the supplements were found to have a similar chance of developing AMD compared with people not taking the supplements. The other 19 studies recruited people with AMD and tested various types of vitamins, including lutein and zeaxanthin, against placebo or no treatment. These studies were smaller than the prevention trials, most were of short duration with patients being followed for less than 2 years. The evidence was mixed but one large study from the USA, called AREDS, had follow-up of over 5 years and found that a combination of vitamin C, E, carotenoids, and zinc may slow progression in people with a diagnosis of AMD. The data from AREDS suggest that there would be approximately 4 fewer cases of progression to late AMD for every 1000 people with very early signs of AMD, who are at low risk of progression, if they take the combination of vitamins used in that trial. In people who already have moderate AMD and are, therefore, at high risk of progression this benefit would rise to approximately 80 fewer cases of progression for every 1000 people taking the vitamins. However, it’s important to note that the carotenoid used in AREDS was beta-carotene and there are concerns about its safety in people who smoke. A later study by the same investigators suggested that beta-carotene could be replaced by lutein and zeaxanthin. Vitamin supplements are generally regarded as safe but there was limited information from these studies on harms. However, evidence from other Cochrane Reviews suggests that mortality in people who take vitamins is generally similar compared with people who do not, with the exception of vitamin E and beta-carotene which are associated with a small increased risk of mortality. In summary, our reviews show that taking vitamin supplements (vitamin C, E or beta-carotene) is unlikely to prevent the development of AMD but a combination of antioxidant vitamins as used in AREDS may slow down the progression of the disease in people with a diagnosis of AMD.

John: If you would like to read more about AREDS and the other studies in Jenny’s reviews, you can find both reviews online at Cochrane Library dot com with a simple search for 'antioxidant vitamin and mineral supplements for AMD'.